Rather than means test it per se (which is a poison chalice for politicians) why not make it that you have to actually retire in order to get it - you must be doing less than, say, 15 hours full time work a week or something.
Good idea but how do you account for people with 'passive' income streams.
My plan (universe laughs) is to have bunch of unencumbered assets producing income by the time I retire. I don't expect there to be any state pension for me but if there is I'll take it. Because I've paid what I think is way too much tax most of my life and any chance to get a cent back legally I'll take it.
As the vikings were wont to say, the gods use men to amuse them. Do not announce your plans - they may hear you and decide to interfere just for the fun of it!
Totally agree with you about tax; as for passive income, if you have made provision for yourself then good luck to you. I would ignore it - it gets taxed in any case. However, I suppose the 'fairness' whiners will not like that (since their definition of fairness is usually the illogical equality of outcome) but for me, I would say active work in paid employment (the idea being to force you to leave the work force, opening space for others as well as ensuring a more reasonable basis for paying the pension) defined by the IRD using your tax records.